Detailed Description

-version
Derive CI versions from the highest supported SemVer tag in the repository.

Keep this helper and test_version.py identical across Buildbot Debian publishers.
Only vX.Y.Z and vX.Y.Z-dev.K (optionally with build metadata) are release tags.
Snapshots use X.Y.(Z+1)-0.N or X.Y.Z-dev.K.N in SemVer, and replace the
prerelease separator with '~' and 'dev.' with 'dev' for Debian. Metadata and
commit hashes do not affect either version. N counts tag..HEAD commits; only
commit identity, not a zero count, makes a build an exact tagged release.